In recent years, a jig for masking areas other than the area subjected to a soldering process, has been frequently used in a soldering procedure performed with a flow solder bath in print-circuit board manufacturing. When such a mask jig (referred to as dip pallet or carrier pallet) is repeatedly used, flux accumulates and adheres onto the surface of the mask jig, thus deteriorating the performance of the jig. Therefore, it is necessary to periodically clean the mask jig.
Generally, the cleaning process is performed by dipping the cleaning object in a solvent. Therefore, a large amount of solvent is used, which inevitably leads to increased costs. Furthermore, a huge workload is inflicted on the worker.
There is known a method of spraying the solvent onto the cleaning object in a device, instead of dipping the cleaning object in the solvent. However, this method also requires a large amount of solvent.
As a technology for solving the above problems, there is known a dry type cleaning device for cleaning a cleaning object by causing the flying cleaning medium to contact the cleaning object.
Patent documents 1 and 2 disclose a cleaning method of causing a cleaning medium to collide with a cleaning object that is contacting an opening formed in the side surface of a cylindrical container. Specifically, the cleaning medium is caused to fly in the circumferential direction in the container by a revolving airflow of a compressed air current.
However, in this method, because the revolving airflow is formed by the compressed air current, the cleaning medium leaks out of the container when the cleaning object is separated from the opening.
To address this problem, patent document 1 has a net member provided at the opening to prevent the cleaning medium from leaking outside. However, other problems arise by providing the net member, such as a decrease in the energy when the cleaning medium collides with the cleaning object, and a decrease in the cleaning performance as the cleaning medium gets caught in the net member.
In patent document 2, an opening/closing lid for blocking the opening is provided to prevent the cleaning medium from leaking outside. However, when the cleaning object is separated from the opening, the opening/closing lid needs to be quickly moved to block the opening. Thus, excessive attention and workload is required of the worker. Furthermore, the mechanism is complex and hard to operate, and is prone to break down.
In view of the above, the applicant of the present application proposed the following dry type cleaning device (Japanese Patent Application No. 2010-175687). Specifically, a suction unit is connected to a case. While a cleaning object is blocking the opening of the case, a revolving airflow is generated by an air current flowing into the case from outside the case via a ventilation path. Thus, thin flakes of the cleaning medium are caused to fly. Furthermore, a net-type porous member is provided, which allows air and dust to pass into the case but does not allow the cleaning medium to pass outside the case, so that the cleaning medium stays in the area where the revolving airflow is formed. Accordingly, the cleaning medium continues to fly around by the revolving airflow.
According to this dry type cleaning device, even when the cleaning object is separated from the opening, the air pressure in the ventilation path becomes the same as the atmospheric pressure, so that the revolving airflow disappears, and a large amount of the outside air enters the case through the opening by negative pressure caused by suctioning. Accordingly, the cleaning medium in the case is suctioned to the porous member, so that the cleaning medium stays in the case and does not leak outside through the opening.
However, it has been found that in the above-described prior application of the applicant of the present application, when the opening is separated from the cleaning object when the cleaning process has been completed, the cleaning medium sometimes flies outside through the opening, due to an airflow that directly flows into the opening from the air inlet (ventilation path) together with the revolving airflow in the case.
At the very moment when the opening is separated from the cleaning object, it is considered that there are cases where the speed of the airflow flowing into the case through the ventilation path is higher than that of the airflow flowing into the case through the opening. That is to say, there may be a moment where the inertial flow of the cleaning medium flying toward the opening caused by the airflow entering from the ventilation path is faster than the airflow entering the case through the opening, during the time period before the airflow entering the case through the opening reaches a speed that is fast enough to keep the cleaning medium in the case.
It is not preferable for the cleaning medium to fly out from the opening in consideration of pollution and safety of the working environment.
After the cleaning is completed, the cleaning medium does not fly out from the opening if the ventilation path is blocked before separating the opening from the cleaning object. However, if the ventilation path needs to be blocked after the cleaning process, troublesome operations are required of the worker. Besides, if the worker forgets to block the ventilation path, this problem cannot be solved.
Patent Document 1: Japanese Laid-Open Patent Application No. H4-83567
Patent Document 2: Japanese Laid-Open Patent Application No. S60-188123
Patent Document 3: Japanese Laid-Open Patent Application No. 2009-226394